The way I look at big purchases is to get up front what would be hard to upgrade at a later date. For a house, it is easier to add fancy new counter tops at a later date, but is relatively harder to add additional square footage.
In your case, I think I agree with NRA4Life. It seems like it would be easier to upgrade the tuning plates at a later date, but relatively more difficult to upgrade your fire box.
Disclaimer: I don't have a fancy smoker yet. I'm just a simple UDS guy for now, so I've got no real world experience in this particular matter.